Regulating device for gas burners

ABSTRACT

The invention relates to a control means for gas burners. Control means for gas burners are used for supplying a gas flow and a combustion air flow to a burner. In this procedure, the gas flow is adjustable in dependence on the combustion air pressure. In the case of known control means, pressure measurement is effected by means of a diaphragm, i.e. pneumatically. This pneumatic pressure measurement restricts the scope of application of known control means. 
     In the case of the control means according to the invention, there is provided a sensor ( 16 ) which generates an electric or electronic signal  19  which is used for adjusting the gas valve  11  (FIG.  1 ).

BACKGROUND OF THE INVENTION

This invention relates to a control means for a gas burner system. Thecontrol means supplies a gas flow and a combustion air flow to the gasburner. The control means adjusts the gas flow through a gas valve thatis dependent on the combustion air pressure.

Control means for gas burners are known in the prior art. In a knowncontrol means, a determination of the pressure is found by means of adiaphragm, or pneumatically. See EP 0 390 964 A1. The gas valve, basedon this pressure determination, controls the gas flow. There are severaldisadvantages to the pneumatic way that restrict the application rangeof known control means. For instance, the hysteresis properties of thediaphragm and the forces acting between the diaphragm and the gas valverestrict the working range. Furthermore, the interaction between thesmall actuating forces and the operating tolerances of the diaphragmrestrict the application range because of disturbing influences, such astemperature variations.

SUMMARY OF THE INVENTION

The present invention is a new kind of control means for a gas burnersystem. The embodiments described herein present a control means for gasburners that solves the problem of a restricted application range.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a first embodiment of a control means for a gas burner system,and

FIG. 2 is a second embodiment of a control means for a gas burnersystem.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a control means for a gas burner system. A gasstream and a combustion air stream are supplied to a gas burner (notrepresented).

In FIG. 1 a first line 10 supplies the gas stream to the gas burner. Thegas stream in the first line 10 flows from a valve 11 to a gas nozzle15.

A second line 12 supplies the combustion air stream to the gas burner.The combustion air in the second line 12 flows from a blower 13. Thesecond line 12 contains a throttle point 14 upstream of the gas nozzle15 and the blower 13.

The gas nozzle 15 closes the first line 10 in the range of the secondline 12. The gas stream in the first line 10 exits from the nozzle 15into the second line 12. Therefore, a gas/air mixture exists downstreamof the gas nozzle 15 in the direction of the combustion air stream.

The embodiment illustrated by FIG. 1 provides a 1:1 gas-air coupledcontrol. An electric or electronic sensor 16 provides the combined 1:1gas/air mixture regulation. The sensor 16 functions as a differentialpressure sensor, of the flow meter or anemometer type.

The sensor 16 is connected to the first line 10 at a measuring point 17.The measuring point 17 is positioned upstream of the gas nozzle 15. Thesensor 16, also, has a reference pressure, which is the combustion airpressure. The FIG. 1 embodiment does not require a connection betweenthe sensor 16 and the second line 12, particularly if the sensor 16 anda combustion air stream inlet are inside the same housing.

The FIG. 1 embodiment of the control means provides a 1:1 gas-aircoupled control, in which the gas pressure equals the referencepressure. If the sensor 16 is a flowmeter or anemometer, then the flowthrough the sensor 16 is zero. For example, if the gas pressuredecreases compared to the combustion air pressure, the sensor 16 causesthe gas stream to flow in the first line 10. The sensor 16 can establishthe pressure ratios between the combustion air pressure and the gaspressure based on the rate of flow.

The sensor 16 generates a signal 19 based on the pressure differentialthat is used for adjusting the gas valve 11. According to FIG. 1, thesignal 19 is fed to a control unit 20. The control unit 20 is eitheropen-loop or closed-loop. The control unit 20 provides a control signal21 to an actuator 22 of the gas valve 11.

Thus, in FIG. 1, if the sensor 16 detects a pressure difference of zerobetween the reference pressure and the gas pressure, the signal 19 willcorrespond to a pressure difference of zero, and the gas valve 11 willnot adjust the gas flow in the first line 10. However, if the sensor 16detects a higher reference pressure than the gas pressure, the gas valve11 will increase the gas flow in the first line 10. This is accomplishedby the control unit 20 generating the control signal 21 for the actuator22 of the gas valve 11, and resetting the signal 19 to correspond to apressure difference of zero.

The FIG. 2 embodiment of the control means provides a 1:N gas-aircoupled control, so a transformation ratio between the gas flow and thecombustion air flow, or the gas pressure and the combustion airpressure, can be obtained.

In FIG. 2, the signal 19 is balanced with an auxiliary signal 24 in asumming means 23 to provide the transformation ratio. The summing means23 balances the signal 19 with the auxiliary signal 24 before the signal19 is fed to the control unit 20. The summing means 23 generates anoutput signal 25. The output signal 25 is supplied to the control unit20. The output signal 25 is an additive overlay, or superimposition, ofthe signal 19 and the auxiliary signal 24.

The auxiliary signal 24 is functionally dependent on a rotational speedof the blower 13. An evaluation means 26 generates the auxiliary signal24 based on a rotational speed signal 27 of the blower 13. Thus, sincethe auxiliary signal 24 is functionally dependent on the rotationalspeed of the blower 13, the auxiliary signal 24 is also dependent on thecombustion air flow, or the combustion air pressure, respectively.

There are alternatives to the FIG. 2 embodiment for generating theauxiliary signal 24. For example, it is not necessary that the auxiliarysignal 24 be dependent on the rotational speed of the blower 13. Rather,an additional sensor (not represented) could generate the auxiliarysignal 24. Consequently, gas-adaptive control can be accomplished withthe output signal of a smoke gas sensor as the auxiliary signal 24.

The evaluation means 26 can generate a multiplication factor fordetermining the transformation ratio between the gas flow and thecombustion air flow . The transformation ratio can be varied byadjusting the multiplication factor. Thus, the higher the multiplicationfactor, the higher the transformation ratio.

What is claimed is:
 1. A control means for a gas burner system, the gasburner system including a first line through which a gas stream flowsfrom a gas valve to a gas nozzle, and a second line through which a fanforces a combustion air stream, the gas nozzle opening into the secondline downstream from a throttle point, the control means comprising, incombination: a measuring point on the first line, the measuring pointpositioned upstream from the gas nozzle; a sensor coupled to themeasuring point and to a reference point for providing the sensor with areference pressure, the sensor generating a signal indicating a pressuredifferential; and a control unit to provide a control signal to anactuator for controlling the gas valve.
 2. The control means of claim 1,wherein the sensor is not directly coupled to the second line.
 3. Thecontrol means of claim 2, wherein the second line includes an inlet, andwherein the inlet and the sensor are co-located in a housing.
 4. Thecontrol means of claim 1, wherein an actuator associated with the gasvalve receives a control signal generated as a function of the signalfrom the sensor indicating the pressure differential.
 5. The controlmeans of claim 1, wherein the sensor providing a pressure differentialis a flow meter.
 6. A control means for a gas burner system, the gasburner system including a first line through which a gas stream flowsfrom a gas valve to a gas nozzle, and a second line through which a fanforces a combustion air stream, the gas nozzle opening into the secondline downstream from a throttle point, the control means comprising, incombination: an evaluation means for generating an auxiliary signal, theauxiliary signal based on a detected auxiliary parameter; a sensorcoupled to a measuring point on the first line and providing a signalindicating a differential pressure between the measuring point and areference point; a summing means for balancing the signal of the sensorwith the auxiliary signal to generate an output signal; and an actuatoroperative to receive the output signal and to control the gas valvebased on the output signal.
 7. The control means of claim 6, wherein thesensor is not directly coupled to the second line.
 8. The control meansof claim 6, wherein the second line includes an inlet, and wherein theinlet and the sensor are co-located in a housing.
 9. The control meansof claim 6, wherein the auxiliary parameter depends on a rotationalspeed of the blower.
 10. The control means of claim 6, wherein theauxiliary parameter is based on an output signal from a smoke gassensor.
 11. The control means of claim 6, wherein the evaluation meansspecifies a variable transformation ratio between the gas stream and thecombustion air stream.
 12. A method for controlling a gas-air mixture toa gas burner system, the gas burner system including a first linethrough which a gas stream flows from a gas valve to a gas nozzle, and asecond line through which a fan forces a combustion air stream, the gasnozzle opening into the second line downstream from a throttle point,comprising in combination: providing a signal indicating a differentialpressure between a first line and a reference point; and controlling anactuating drive based on the signal, thereby controlling the gas valve.13. The method of claim 12, wherein the differential pressure ismeasured between a first measuring point positioned upstream from thegas nozzle and a reference point, the reference point providing areference pressure.
 14. The method of claim 12, wherein controlling anactuating drive includes receiving the signal indicating thedifferential pressure and providing a control signal to the actuatingdrive.
 15. The method of claim 12, wherein the sensor is a flowmeter.16. The method of claim 12, wherein the sensor is not directly coupledto the second line.
 17. The method of claim 16, wherein the second lineincludes an inlet, and wherein the inlet and the sensor are co-locatedin a housing.
 18. A method for controlling a gas-air mixture to a gasburner system, the gas burner system including a first line throughwhich a gas stream flows from a gas valve to a gas nozzle, and a secondline through which a fan forces a combustion air stream, the gas nozzleopening into the second line downstream from a throttle point,comprising in combination: providing an auxiliary signal based ondetecting an auxiliary parameter; providing a signal indicating adifferential pressure between the first line and a reference point;balancing the auxiliary signal with the signal indicating thedifferential pressure to provide an output signal; and controlling anactuating drive based on the output signal, thereby controlling the gasvalve.
 19. The method of claim 18, wherein the auxiliary parameterdepends on a rotational speed of the blower.
 20. The method of claim 18,wherein the auxiliary parameter is based on an output signal from asmoke gas sensor.
 21. The method of claim 18, wherein balancing theauxiliary signal with the signal indicating the differential pressure toprovide the output signal allows a gas-air mixture to be set to avariable transformation ratio, wherein a variable transformation rationis specified by an evaluation means, and wherein the evaluation meansprovides the auxiliary signal.
 22. The method of claim 18, wherein thevariable transformation ratio is between the gas stream and thecombustion air stream.
 23. The method of claim 18, wherein the signalindicating the differential pressure is provided by a sensor that is notdirectly coupled to the second line.
 24. The method of claim 23, whereinthe second line includes an inlet, and wherein the inlet and the sensorare co-located in a housing.